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8 mgfL until Day 20, when 0 dropped to less than These result�e somewhat biased by the geometry and
<br /> 1 mg/L.The D.O.level approximately 0.5 m downgradi- ORC mass of the pencil network,which could not pro-
<br /> ent of the pencils (PL-3) was also high initially (10 mg/ duce sufficient oxygen to support the degradation of
<br /> L on Day 13), but decreased to less than 1 mg/L on B/1: A more extensive network of pencils might have
<br /> Day 20. These D.O. concentrations are within the led to complete degradation of the B/1:
<br /> expected range discussed above; however, the initial Overall, this field study indicates that ORC can be
<br /> high release rate from the pencils in the field was main- used to introduce dissolved oxygen into ground water
<br /> tained for a period of time greater than predicted by flowing past it. Furthermore, the study indicates that
<br /> the laboratory data provided by PRL. the enhancement of the D.O.content of the ground water
<br /> Figures 8b and 8c show the benzene and toluene by ORC can lead to biodegradation of at least 4 mg/L
<br /> concentrations, respectively, along the Pencil Line.The each of benzene and toluene dissolved in ground water.
<br /> benzene concentrations decreased along the transport Such concentrations are typical of those encountered at
<br /> path more significantly than in the Aquifer Line, but sites contaminated with petroleum hydrocarbons;thus the
<br /> the decrease was not as sharp as in the case of the ORC- controlled studies conducted as part of this project suggest
<br /> Concrete Line. Benzene concentration appeared to that there is promise for the use of ORC in passive (non-
<br /> decrease by 50 to 85 percent along the flow path relative pumping) systems to enhance in situ biodegradation of
<br /> to the concentration at PL-1. Prior to Day 33, toluene BTEX contaminants at such sites. Additional work is
<br /> behavior was similar to benzene, with a sharp decline necessary to examine the long-term behavior of the ORC
<br /> of 50 to 85 percent along the Pencil Line.After Day 33, and to evaluate other methods of contacting ORC with
<br /> the toluene concentration at PL-1 declined significantly contaminated ground water.
<br /> probably due to denitrification. Although the absolute
<br /> decrease in toluene concentration was not as great after Acknowledgments
<br /> Day 33, the decline was significant relative to the con-
<br /> centration measured at PL-1. Funding for this work was provided in part by a
<br /> contract from Plant Research Laboratories, Corona del
<br /> Mar, California. Additional support was provided by
<br /> the Waterloo Centre for Groundwater Research at the
<br /> Summary and Conclusions
<br /> University of Waterloo, Waterloo, Ontario. Other sup-
<br /> A field test was conducted at the Borden site to port was provided by the Groundwater and Soil Reme-
<br /> evaluate the applicability of an oxygen-releasing com- diation Program sponsored by Environment Canada
<br /> pound (ORC), in briquet and powdered form, to the and Energy,Mines,and Resources Canada.The authors
<br /> remediation of ground water contaminated with gaso- would like to thank Eric Mewhinney, Dave Thomas,
<br /> line components.The fate of the solutes was monitored and Paul Johnson for their diligent field support,as well
<br /> along four lines of monitoring points and wells. Two as other University of Waterloo faculty, staff, and field
<br /> lines studied the behavior of the solutes upgradient and technicians that participated in this project.
<br /> downgradient of two large-diameter well screens filled
<br /> with ORC-concrete briquets or concrete briquets. One Editor's Note: The use of brand names in peer-reviewed
<br /> line was used to study the solute behavior upgradient papers is for identification purposes only and does not
<br /> and downgradient of columns of ORC powder placed constitute endorsement by the authors,their employers,
<br /> in the saturated zone.The remaining line was a control. or the Ground Water Publishing Co.
<br /> The results for the ORC in briquet form indicated
<br /> that the ORC-concrete briquets raised the D.O. level
<br /> in the contaminated ground water which passed by References
<br /> them. During part of the experiment, the benzene and Acton, D.W., and J.F. Barker. 1992. In situ biodegradation
<br /> toluene concentrations within and downgradient of the potential of aromatic hydrocarbons in anaerobic ground-
<br /> screen decreased significantly,apparently due to aerobic waters.J. Contaminant Hydrology 9: 325-52.
<br /> Aelion,C.M.,and P.M.Bradley.1991.Aerobic biodegradation
<br /> degradation resulting from the added oxygen. After the
<br /> injection of benzene and toluene ceased,the D.O.levels potential of subsurface microorganisms from a jet fuel-
<br /> rose to 45.6 m contaminated aquifer.Applied and Environmental Micro-
<br /> rose which is near the D.O. predicted by biology 57, no. 1: 57-63.
<br /> laboratory release rates under the field conditions Allen, R.M. 1991. Fate and transport of dissolved monoaro-
<br /> (55 mg(L) within the briquet screen,indicating that the matic hydrocarbons during steady infiltration through soil.
<br /> OZ production continued after at least 10 weeks. Ph.D.thesis,Department of Earth Sciences,University of
<br /> The results for the ORC in pencil form indicated Waterloo.
<br /> that the pencils also released oxygen to water.However, APHA,AW WA,and WPCF.1985.Azide modification to iodo-
<br /> at least in the configuration tested,the D.O.values were metric method for dissolved oxygen determination,Section
<br /> not as high as those observed in the briquet section of 421b. In Standard methods for the examination of water
<br /> the experiment. Furthermore, it appeared that the and wastewater. 16th ed.,418.19.Washington,D.C.:Ameri-
<br /> oxygen generated by the pencils was consumed by Armstrong,A.Q.,R.E.Hodson,H.M.Hwang,and D.L.Lewis.
<br /> microbial metabolism almost immediately. There was 1991.Environmental factors affecting toluene degradation
<br /> significant degradation of benzene and toluene, but in ground water at a hazardous waste site.Environ. Tosicol.
<br /> unlike with the briquets, not to below detection limit. Chem. 10: 147-58.
<br /> WINTER 1994 GWMR a 127
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